1. Are all old companions returning in some fashion? 2. Are all old companions returning as potential companions? 3. Are all old companions staying with the same faction? 4. Are any old companions having their VA's recast? 5. Are all old companion romances available to continue? 6. Are any old companions available to be romanced that couldn't before? 7. Are the old & new companions available to be recruited class-dependent? 8. What happens to Treek & HK-51? 9. Will companions have their combat roles expanded? 10. Will companions gain new conversation quests? 11. Will companions gain new more-than-conversation quests?

Thanks.

You are on the right track! We will be talking about quite a few of these, plus a few other details you don't have listed here. It is worth noting that if a question starts dipping into spoiler territory, we probably won't answer it or if we do it will be in a general sense.